U.S. patent number 8,330,697 [Application Number 11/821,808] was granted by the patent office on 2012-12-11 for methods and liquid crystal display devices that reduce/avoid tearing effects in displayed images.
This patent grant is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Jae-hoon Lee.
United States Patent |
8,330,697 |
Lee |
December 11, 2012 |
Methods and liquid crystal display devices that reduce/avoid
tearing effects in displayed images
Abstract
Methods and related liquid crystal display devices are disclosed
that reduce/avoid a tearing effect in displayed images. A scan time
of a scan clock signal of a display is detected. A write time of a
write clock signal that writes data into a memory for display on
the display is detected. The write time is regulated in response to
a comparison of the scan time of the scan clock signal to the write
time of the write clock signal.
Inventors: |
Lee; Jae-hoon (Gyeonggi-do,
KR) |
Assignee: |
Samsung Electronics Co., Ltd.
(KR)
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Family
ID: |
39628316 |
Appl.
No.: |
11/821,808 |
Filed: |
June 26, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080174540 A1 |
Jul 24, 2008 |
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Foreign Application Priority Data
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Jan 23, 2007 [KR] |
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10-2007-0007251 |
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Current U.S.
Class: |
345/99 |
Current CPC
Class: |
G09G
5/395 (20130101); G09G 2340/0435 (20130101) |
Current International
Class: |
G09G
3/36 (20060101) |
Field of
Search: |
;345/98,99,87,204,213,690 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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09-023441 |
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Jan 1997 |
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JP |
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2002-132237 |
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May 2002 |
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JP |
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2002-215081 |
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Jul 2002 |
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JP |
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2005-124167 |
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May 2005 |
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JP |
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WO 2005004103 |
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Jan 2005 |
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WO |
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WO 2005/073955 |
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Aug 2005 |
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WO |
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Other References
Chinese First Office Action Corresponding to Chinese Patent
Application No. 2008100085606; Dated: Jul. 13, 2011; 9 pages,
English Translation thereof, 12 pages. cited by other .
Chinese Office Action Corresponding to Chinese Patent Application
No. 200810008560.6; Dated: Feb. 23, 2012; Chinese Text, 7 pages,
English Translation Thereof, 9 pages. cited by other.
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Primary Examiner: Nguyen; Chanh
Assistant Examiner: Yang; Kwang-Su
Attorney, Agent or Firm: Myers Bigel Sibley & Sajovec,
P.A.
Claims
What is claimed is:
1. A liquid crystal display device comprising: a liquid crystal
display panel; a controller that is configured to receive image
data from circuitry external to the liquid crystal display device
and to generate a write clock signal defining a write time; and a
liquid crystal display driver that is configured to store image
data from the controller at a rate defined by the write time of the
write clock signal, to generate a scan clock signal having a scan
time, and to generate an image signal in response to the stored
image data, the image signal having a rate defined by the scan time
of the scan clock signal, wherein the liquid crystal display driver
scans the image signal into the liquid crystal display panel at the
rate defined by the scan time of the scan clock signal to display
an image on the liquid crystal display panel, wherein the
controller regulates the write time of the write clock signal in
response to a comparison of the scan time of the scan clock signal
to the write time of the write clock signal, wherein the controller
detects the write time of the write clock signal, detects the scan
time of the scan clock of the scan clock signal, compares the scan
time of the scan clock signal to the write time of the write clock
signal, and adjusts the write time of the write clock signal in
response to the comparison, and wherein the controller responds to
the write time being greater than the scan time by reducing the
write time, and responds to the write time being less than the scan
time by increasing the write time, so that the controller adjusts
the write time of the write clock signal to be equal to the scan
time of the scan clock signal.
2. The liquid crystal display device of claim 1, wherein: the
liquid crystal display driver comprises a memory; and the liquid
crystal display driver writes the image data from the controller
into the memory at the rate defined by the write time of the write
clock signal.
3. The liquid crystal display device of claim 2, wherein the liquid
crystal display driver further comprises an oscillator that
generates the scan clock signal.
4. The liquid crystal display device of claim 2, wherein the liquid
crystal display driver further comprises: a source driver that is
configured to read the image data from the memory and to output the
image signal to the liquid crystal display panel at a rate defined
by the write time of the write clock signal; and a gate driver that
is configured to respond to the write clock signal to control a
position where the image signal is to be displayed.
5. The liquid crystal display device of claim 1, wherein: the
liquid crystal display driver comprises a memory; the image data
comprises color information; and the liquid crystal display driver
is further configured to output the color information from the
memory to the liquid crystal display panel to control colors of
pixels of the liquid crystal display panel in response to the scan
clock signal.
6. The liquid crystal display device of claim 5, wherein the liquid
crystal display driver is further configured to repetitively
display the color information for an entire screen of pixels of the
liquid crystal display panel at a rate corresponding to the scan
time, and to repetitively write to the memory the color information
for an entire screen of pixels of the liquid crystal display panel
at a rate corresponding to the write time.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION
This application claims the benefit of Korean Patent Application
No. 10-2007-0007251, filed on Jan. 23, 2007, in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
FIELD OF THE INVENTION
The present invention relates to methods of displaying images and
related liquid crystal display (LCD) devices.
BACKGROUND OF THE INVENTION
Liquid crystal displays (LCDs), such as thin film transistor LCDs,
are increasingly being used in electronic devices, such as in
mobile phones. One design constraint on the use of LCDs is their
ability to provide sufficiently compact and low-cost displays
capable of clearly displaying moving images. New controllers have
emerged that are targeted at specifically controlling the display
of moving images on LCDs. However, these specialized controllers
may be prohibitively expensive for use in some electronic devices,
such as in some mobile phones. Moreover, the display architecture
may require the use of a conventional controller along with the
specialized controller. The use of two controllers may lead to the
use of interrupt-based processing for large amounts of image data,
which may decrease the efficiency at which moving images are
processed and may increase the complexity of the control
software.
FIG. 1A illustrates a conventional LCD device 100. Referring to
FIG. 1A, the LCD device 100 includes an LCD panel 101, an LCD
driver 110, and a controller 120.
The controller 120 controls the display of image data on the LCD
panel 101. The controller 120 generates and outputs control
signals, which can include a chip selection "CS" signal, a write
clock "WR" signal, a DATA signal, and the like.
The CS signal is used to select and enable individual pixels on the
LCD panel 101. The WR signal is used to write data (e.g., image
data), which is received from circuitry external to the LCD device
100, to a memory 113 included in the LCD driver 110. Hereinafter,
the write clock signal will be referred to as CLK_W. The DATA
signal refers to image data that is generated from data that is
received from circuitry that is external to the LCD device 100.
The LCD driver 110 includes a source driver/gate driver 111, the
memory 113, and an oscillator 115.
The image data from the controller 120 is written into the memory
113. The write operation is performed using the write clock signal
CLK_W which is output by the controller 120, and which may be used
as an internal operational clock for the controller 120.
The source driver/gate driver 111 reads the image data from the
memory 113 and outputs therefrom an image signal to the LCD panel
101 in response to a control signal which is generated by the
controller 120.
The source driver/gate driver 111 also responds to the control
signal transmitted from the controller 120 by controlling
positioning of the image signal on the LCD panel 101. Such
structure and operation of the source driver/gate driver 111 is
well known to those of ordinary skill in the art and, accordingly,
further details thereof will be omitted for brevity.
The oscillator 115 generates a scan clock signal CLK_FLM which is
used by the LCD driver 110 to scan an image signal from the source
driver/gate driver 111 onto the display of the LCD panel 101. The
scanning operation using the scan clock signal CLK_FLM will be
described with reference to FIG. 1B.
FIG. 1B is a timing diagram that illustrates relative timing
between the write clock signal CLK_W and the scan clock signal
CLK_FLM and operation thereof, and further illustrates a tearing
effect that occurs during the operation of the LCD device 100.
In the conventional LCD device 100 of FIG. 1A, the write clock
signal CLK_W, used for regulating writing of image data into the
memory 113, and the scan clock signal CLK_FLM, used to scan image
data on the display of the LCD panel 101, are not synchronized to
one another.
Referring to FIG. 1B, when the scan clock signal CLK_FLM is low,
the image signal is scanned to pixels in the LCD panel 101. A
bottom pixel line is referred to as Line 1 and a top pixel line is
referred to as Line 160. When the scan clock signal CLK_FLM
generated by the oscillator 115 is low, the LCD driver 110 performs
a scanning operation from Line 1 of the LCD panel 101 up to Line
160 of the LCD panel 101.
When the write clock signal CLK_W is low, the image data
transmitted by the controller 120 is written to the memory 113. The
write operation is performed in units of frame data. In other
words, the image data is written during the low level period of the
write clock signal CLK_W and single frame data is written to the
memory 113 during a single interval of the low level period. For
reference, a general scan clock signal CLK_FLM can have a frequency
of 60 Hz and a general write clock signal CLK_W can have a
frequency band of 15-30 Hz. Thus, when the scanning operation is
performed three or four times, the write operation is performed
once. When new image data is not input, the LCD driver 110 scans
stored image data and displays the image data on the LCD panel
101.
In the LCD device 100, the write clock signal CLK_W and the scan
clock signal CLK_FLM are not synchronized with each other.
Moreover, the duration of the low level period of the write clock
signal CLK_W can be constant, and an operating frequency band and
an active period are not matched. Consequently, at a point "a" in
FIG. 1B, the write clock signal CLK_W and the scan clock signal
CLK_FLM, overlap each other at timing coordinates (a, X).
FIG. 1C illustrates an image that is displayed on the LCD panel 101
and which exhibits a tearing effect as a result of the relative
signal timing shown in FIG. 1B.
Before time "a", the LCD driver 110 scans the image data that was
previously stored in the memory 113. However, after time "a", the
LCD driver 110 scans image data that is newly stored in the memory
113 after the time "a". In the example of FIG. 1C, the LCD driver
110 displays white pixel color from Line 1 to a line X in response
to the image data that was stored in the memory 113 before time
"a", and displays black pixel color from the line X to Line 160 in
response to other image data that was stored in the memory 113
after time "a".
Accordingly, a tearing effect in the displayed image occurs at the
line X of the LCD panel 101. The tearing effect corresponds to a
lack of logical association among image data that is displayed on
the LCD panel 101. In the present example, the white pixels are
associated with the same image, however the black pixels are
associated with another image that is intended to displayed
subsequent to the display of the white image. The timing
intersection of the scan clock signal CLK_FLM and the write clock
signal CLK_W corresponds to the location of the tearing effect on
the image that is displayed on the LCD device 101.
FIG. 2A illustrates a conventional LCD device 200 device that is
configured to attempt to prevent the occurrence of a tearing
effect.
The LCD device 200 includes an LCD panel 201, an LCD driver 210,
and a controller 220, which can be configured to operate in a
similar manner to the LCD panel 101, the LCD 110, and the
controller 120 described above, and, accordingly, further
description of these components is omitted for brevity.
In an attempt to prevent a tearing effect in a displayed image, the
LCD device 200 includes a synchronization processing unit 222 in
the controller 220. The operation of the synchronization processing
unit 222 will be described in detail with reference to FIG. 2B.
FIG. 2B is a block diagram that illustrates various operations of
the controller 220 and the LCD driver 210.
Referring to FIG. 2B, the controller 220 of the LCD device 200
receives a signal FLM_Vsync providing synchronization information
for a scan clock signal from the LCD driver 210. The
synchronization processing unit 222 of the controller 220 is
configured to synchronize the write clock signal CLK_W with the
scan clock signal CLK_FLM using the received signal FLM_Vsync. The
synchronization processing unit 222 synchronizes the scan clock
signal CLK_FLM and the write clock signal CLK_W in response to each
transition of the write clock signal CLK_W from high to low.
In the conventional LCD devices 100 and 200 illustrated in FIG. 1A
and FIG. 2A, the controllers 120 and 220 cannot perform other
operations (i.e., stop carrying-out other operations) while they
process image data. Because other operations are interrupted while
image data is processed, the processing can be referred to as
interrupt processing.
If such interrupt processing is to be avoided, thereby avoiding
interruption of other operations in response to the input of a
signal FLM, the LCD device 200 illustrated in FIG. 2A can include a
separate processor that is configured to synchronize the write
clock signal CLK_W in response to the input signal FLM_Vsync. The
separate processor may be included in the synchronization
processing unit 222 of the LCD device 200.
FIG. 2C is a timing diagram illustrates relative timing between the
write clock signal CLK_W and the scan clock signal CLK_FLM during
the operation of the LCD device 200 of FIG. 2A. Referring to FIG.
2C, when the write clock signal CLK_W is synchronized with the scan
clock signal CLK_FLM, an intersecting point "a" between such
signals described in FIG. 1B does not occur and, therefore,
occurrence of the tearing effect may thereby be reduced.
Although the tearing effect is reduced, the inventors of the
present application have determined that the tearing effect may not
be completely prevented, possibly because of a change in the
operating frequency of the scan clock signal CLK_FLM and/or
dispersion of the write clock signal CLK_W generated by the
controller 220.
As described above, in the conventional LCD device 100, the scan
clock signal CLK_FLM and the write clock signal CLK_W are not
synchronized with each other and the write speed of the write clock
signal CLK_W is constant, which results in occurrence of the
tearing effect.
Moreover, although the LCD device 200 can reduce the occurrence of
the tearing effect, the synchronization processing unit 220 needs
to have a separate processor that carries out the signal
synchronization. Furthermore, the tearing effect may not be
completely prevented, possibly because of changes in the operating
frequency of the scan clock signal CLK_FLM and/or dispersion of the
write clock signal CLK_W generated by the controller 220.
SUMMARY OF EMBODIMENTS OF THE INVENTION
Various embodiments of the present invention are directed to
reducing/avoiding the occurrence of a tearing effect in displayed
images, and which may be provided although the signal interfaces to
a display device are subjected to varying frequencies and without
necessitating the use of a plurality of separate processors with a
display driver.
A method of reducing/avoiding a tearing effect in displayed images
can include detecting a scan time of a scan clock signal of a
display, detecting a write time of a write clock signal that writes
data into a memory for display on the display, and regulating the
write time in response to a comparison of the scan time to the
write time.
In some further embodiments, the write time of the write clock
signal may be regulated by adjusting the write time to be equal to
the scan time of the scan clock signal. When the write time is
greater than the scan time, the write time can be reduced in
response to the difference between the write time and the scan
time. When the write time is less than the scan time, the write
time can be increased in response to the difference between the
write time and the scan time.
In some further embodiments, color information can be written to
the memory at a rate that is controlled by the regulated write time
of the write clock signal. The memory can be configured as a
display memory for a liquid crystal display (LCD) driver. The color
information can be scanned from the memory onto a LCD panel. The
color information can be scanned from the memory in response to the
scan clock signal to control colors of pixels of the LCD panel. The
color information for each of the pixels of the LCD panel can be
written to the memory in response to the write clock signal.
In some further embodiments, the color information for an entire
screen of pixels of the LCD panel can be repetitively scanned at a
rate corresponding to the scan time. The color information for an
entire screen of pixels of the LCD panel can be repetitively
written to the memory at a rate corresponding to the write
time.
Some other embodiments of present invention are directed to a LCD
device that includes an LCD panel, a controller, and an LCD driver.
The controller is configured to receive image data from circuitry
external to the LCD device and to generate a write clock signal
defining a write time. The LCD driver is configured to store image
data from the controller at a rate defined by the write time of the
write clock signal, to generate a scan clock signal having a scan
time, and to generate an image signal in response to the stored
image data. The image signal has a rate defined by the scan time of
the scan clock signal. The LCD driver scans the image signal into
the LCD panel at a rate defined by the scan time of the scan clock
signal to display an image on the LCD panel. The controller
regulates the write time of the write clock signal in response to a
comparison of the scan time of the scan clock signal to the write
time of the write clock signal.
In some further embodiments, the controller detects the write time
of the write clock signal, detects the scan time of the scan clock
of the scan clock signal, compares the scan time of the scan clock
signal to the write time of the write clock signal, and adjusts the
write time of the write clock signal in response to the
comparison.
In some further embodiments, the controller adjusts the write time
of the write clock signal to the equal to the scan time of the scan
clock signal.
In some further embodiments, the LCD driver comprises a memory, and
writes image data from the controller into the memory at a rate
defined by the write time of the write clock signal.
In some further embodiments, the LCD driver further includes an
oscillator that generates the scan clock signal.
In some further embodiments, the LCD driver further includes a
source driver that is configured to read the image data from the
memory and to output the image signal to the LCD panel at a rate
defined by the write time of the write clock signal, and includes a
gate driver that is configured to respond to the write clock signal
to control a position where the image signal is to be
displayed.
In some further embodiments, the controller responds to the write
time being greater than the scan time by reducing the write time,
and responds to the write time being less than the scan time by
increasing the write time. The controller may adjust the write time
to be equal to the scan time.
In some further embodiments, the LCD driver includes a memory. The
image data includes color information. The LCD driver is further
configured to output the color information from the memory to the
LCD panel to control colors of pixels of the LCD panel in response
to the scan clock signal. The LCD driver may be further configured
to repetitively display the color information for an entire screen
of pixels of the LCD panel at a rate corresponding to the scan
time, and to repetitively write to the memory the color information
for an entire screen of pixels of the LCD display at a rate
corresponding to the write time.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features and potential advantages of the
present invention will become more apparent by describing in detail
exemplary embodiments thereof with reference to the attached
drawings in which:
FIG. 1A illustrates a conventional liquid crystal display (LCD)
device;
FIG. 1B is a timing diagram that illustrates relative timing
between the write clock signal CLK_W and the scan clock signal
CLK_FLM and operation thereof, and further illustrates a tearing
effect that occurs during the operation of the LCD device of FIG.
1A;
FIG. 1C illustrates an LCD screen that may occur as a result of a
tearing effect caused by the signal timing of FIG. 1B;
FIG. 2A illustrates a conventional LCD device that is configured to
attempt to prevent the occurrence of a tearing effect;
FIG. 2B is a block diagram that illustrates various operations of
the controller and the LCD driver illustrated in FIG. 2A;
FIG. 2C is a timing diagram that illustrates relative timing
between the write clock signal CLK_W and the scan clock signal
CLK_FLM during the operation of the LCD device of FIG. 2A;
FIG. 3 is a flowchart of methods for reducing/avoiding the tearing
effect according to a first exemplary embodiment of the present
invention;
FIG. 4A illustrates an LCD device configured to reducing/avoid the
tearing effect according to a second exemplary embodiment of the
present invention; and
FIG. 4B is a timing diagram that illustrates relative timing
between the write clock signal CLK_W and the scan clock signal
CLK_FLM during exemplary operation of the LCD device of FIG.
4A.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The present invention is described more fully hereinafter with
reference to the accompanying drawings, in which embodiments of the
invention are shown. This invention may, however, be embodied in
many different forms and should not be construed as limited to the
embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the scope of the invention to those skilled in
the art. In the drawings, the sizes and relative sizes of layers
and regions may be exaggerated for clarity.
It will be understood that when an element or layer is referred to
as being "on," "connected to" or "coupled to" another element or
layer, it can be directly on, connected or coupled to the other
element or layer or intervening elements or layers may be present.
In contrast, when an element is referred to as being "directly on,"
"directly connected to" or "directly coupled to" another element or
layer, there are no intervening elements or layers present. Like
reference numerals refer to like elements throughout. As used
herein, the term "and/or" includes any and all combinations of one
or more of the associated listed items.
It will be understood that, although the terms first, second, etc.
may be used herein to describe various elements, components,
regions, layers and/or sections, these elements, components,
regions, layers and/or sections should not be limited by these
terms. These terms are only used to distinguish one element,
component, region, layer or section from another region, layer or
section. Thus, a first element, component, region, layer or section
discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of
the present invention.
Is The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a," "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, integers,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which the present
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and will not be
interpreted in an idealized or overly formal sense unless expressly
so defined herein.
FIG. 3 is a flowchart of methods for reducing/avoiding a tearing
effect according to a first exemplary embodiment of the present
invention.
Referring to FIG. 3, a write clock signal CLK_W generated by a
controller is detected in operation 301. More particularly, the
active period duration (time) of the write clock signal CLK_W can
be detected. Hereinafter, the active period duration of the write
clock signal CLK_W will be referred to as "write time." The write
clock signal CLK_W is used by the controller to write image data
through a write operation into a memory in the LCD driver.
A scan clock signal CLK_FLM is detected in operation 305. The scan
clock signal CLK_FLM is used by the LCD driver to perform a scan
operation with respect to an LCD panel, so as to scan image data
from the memory into an image that is displayed on the LCD panel.
The active period duration (time) of the scan clock signal CLK_FLM
is detected. Hereinafter, the active period duration of the scan
clock signal CLK_FLM will be referred to as "scan time."
A determination is made in operation 310 as to whether the scan
time of the scan clock signal CLK_FLM and the write time of the
write clock signal CLK_W are equal to each other. If not, a further
determination is carried out in operation 315 as to whether the
write time is greater than the scan time.
When the write time is greater than the scan time, the write time
of the write clock signal CLK_W is reduced in operation 317 to be
equal to the scan time.
When the write time is less than the scan time, the write time of
the write clock signal CLK_W is increased in operation 319 to be
equal to the scan time.
When the scan time and the write time are equal to each other, in
operation 310, the controller writes image data in operation 320 to
the memory of the LCD driver synchronously with the adjusted write
clock signal CLK_W.
The LCD driver then performs in operation 325 a scan operation to
display the image data on the LCD panel synchronously with the scan
clock signal CLK_FLM.
Accordingly, the write time of the write clock signal CLK_W is
adjusted (regulated) in response to the scan time of the scan clock
CLK_FLM, so as to cause the controller to write image data at the
same speed that the LCD driver scans image data onto the LCD panel.
Consequently, an intersecting timing point between the write clock
signal CLK_W and the scan clock signal CLK_FLM is avoided, which
may prevent the occurrence of a tearing effect in the image
displayed in the LCD panel. Moreover, the write clock signal CLK_W
can be dynamically adjusted to respond to changes in the operating
frequency of the scan clock signal CLK_FLM, which can thereby
compensate for signaling changes from circuitry that is external to
the LCD device.
FIG. 4A illustrates an LCD device 400 that is configured to
reduce/avoid occurrence of a tearing effect and a display image in
accordance with a second exemplary embodiment of the present
invention. The LCD device 400 may be configured to operate
according to the methods described above with regard to FIG. 3.
Referring to FIG. 4A, the LCD device 400 includes an LCD panel 401,
an LCD driver 410, and a controller 420. The LCD driver 410
includes a source driver/gate driver 411, a memory 413, and an
oscillator 415.
The source driver/gate driver 411 retrieves image data that is
stored in the memory 413 and outputs, in response thereto, an image
signal to the LCD panel 401 in response to a control signal
generated by the controller 420. The image signal may contain image
data that was received from circuitry external to the LCD device
400, or may include image data that has been further processed to,
for example, cancel noise and/or improve image that will be
displayed. The image signal may be, for example, a
red(R)/green(G)/blue(B) signal.
The source driver/gate driver 411 responds to the control signal
from the controller 420 by controlling positioning of where the
image signal is to be displayed on the LCD panel 401.
The oscillator 415 generates a scan clock signal CLK_FLM that is
used by the LCD driver 110 to scan the image signal from the source
driver/gate driver 411 onto the LCD panel 401 for display.
The controller 420 controls display of the image data onto the LCD
panel 401. The controller 420 may, for example, process image data
that is received from an external complementary
metal-oxide-semiconductor (CMOS) image sensor to generate image
data, and/or it may determine when and how the generated image data
is to be displayed on the LCD panel 401. The controller 120
generates and outputs control signals such as a CS signal, a WR
signal, a DATA signal and the like, so that the image data can be
output to the LCD driver 410 and displayed through the LCD panel
401.
The CS signal is a chip selection signal that is used to select and
enable individual pixels on the LCD panel 401, so that the
individual pixels can be controlled in response to the image data
to display a screen image on the LCD panel 401. The WR signal is a
write clock signal that is used to write data, which is received
from circuitry external to the LCD device 400, into a memory 413 in
the LCD driver 410. As described above, the write clock signal is
referred to as CLK_W. The DATA signal contains image data that is
received from circuitry external to the LCD device 400.
The controller 420 generates the control signals in order to define
which pixels and at what time image data is to be displayed, and
thereby controls the display of the image data on the LCD panel 410
through the LCD driver 410.
The controller 420 receives scan time information FLM for the scan
clock signal CLK_FLM from the oscillator 415. The controller 420
adjusts a write time of the write clock signal CLK_W generated
inside the controller 420 in response to the scan time information
FLM. Adjustment of the write clock signal CLK_W by adjustment of
the write time may, for example, be carried out only once during an
initial stage of displaying a moving image. Alternatively, the
write clock signal CLK_W may be repetitively adjusted, such as
being periodically adjusted at defined intervals.
As described above, the conventional LCD device 200 of FIG. 2A
receives a synchronization information signal FLM_Vsync of the scan
clock signal CLK_FLM in response to activation of the write clock
signal CLK_W. For this reason, the LCD device 200 needs to include
a separate processor to avoid the need for interrupt processing. In
sharp contrast, the LCD device 400 may be configured to operate
without use of a separate processor and while avoiding the need for
interrupt processing. Moreover, by dynamically changing the write
time in response to variation in the scan time, the occurrence of
tearing effect in displayed images may be reduced/prevented.
FIG. 4B is a timing diagram that illustrates relative timing
between the write clock signal CLK_W and the scan clock signal
CLK_FLM during exemplary operation of the LCD device 400
illustrated in FIG. 4A.
According to the present example, the LCD device 400 has a write
time T2 and a scan time T1 which are equal to each other, such that
the speed at which image data is written to the memory 413 is equal
to the speed at which image data is scanned onto the LCD panel 401.
Consequently, the write clock signal CLK_W and the scan clock
signal CLK_FLM may not exhibit the intersecting timing and
intersecting point "a" shown in FIG. 1A. Consequently, the LCD
device 400 may not exhibit a tearing effect in displayed
images.
As described above, when a write clock signal of a display memory
and a scan clock signal for the display are asynchronous relative
to one another, the tearing effect in displayed images can be
reduced/avoided without necessitating the use of a separate
processor for synchronization and interrupt processing. Because the
write time and scan time can be made equal, a tearing effect may be
prevented/reduced in displayed images despite variations in the
frequency of an LCD driver and/or in clock signals.
While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof, it will
be understood by those of ordinary skill in the art that various
changes in form and detail may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
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